A Comprehensive Review of Azelaic Acid Pharmacological Properties, Clinical Applications, and Innovative Topical Formulations.

Azelaic acid (AzA), a saturated dicarboxylic acid, is indicated for the treatment of acne vulgaris, rosacea, melasma, and post-inflammatory hyperpigmentation. Its antimicrobial, anti-inflammatory, and antimelanogenic properties support its use; however, its poor aqueous solubility and limited skin permeability constrain its optimal topical delivery. This review summarizes clinical evidence and advances in formulations-including conventional vehicles, polymeric/lipid nanocarriers, and deep eutectic solvent (DES) systems-to promote more effective and well-tolerated use. Across indications, 15-20% azelaic acid (AzA) formulations produced clinically meaningful improvements with mild, transient local irritation. For acne vulgaris, reductions in inflammatory and noninflammatory lesions were comparable to those of topical retinoids/adapalene, and tolerability was superior in some studies. For rosacea, the 15% gel formulation was comparable to metronidazole in reducing papules, pustules, and erythema while maintaining negligible systemic exposure. In melasma and other dyschromias, 20% cream demonstrated efficacy similar to hydroquinone, exhibiting a favorable safety profile. Advanced delivery systems, including liposomes, niosomes/ethosomes, nanostructured lipid carriers, microemulsions, nanosponges, and DES platforms, increased AzA solubilization, cutaneous deposition, and stability. This enabled dose-sparing strategies and improved adherence. Data on AzA cocrystals and ionic salts suggest additional control over release and irritation. AzA remains a versatile and well-tolerated dermatologic agent whose performance is strongly vehicle-dependent. Rational selection and engineering of carriers, particularly DES-integrated polymeric and lipid systems, can mitigate solubility and permeability limitations, enhance skin targeting, and reduce irritation in the treatment of acne and rosacea.